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[PATCH v40 3/4] Serialize decoded tuples without flattening. 334+ messages / 1 participants [nested] [flat]
* [PATCH v40 3/4] Serialize decoded tuples without flattening. @ 2026-03-09 10:35 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-03-09 10:35 UTC (permalink / raw) So far we used to flatten the tuples produced by logical decoding in order to write them to a temporary file. That means that all the TOASTed attributes ended up in a single chunk of memory. The problem is that even if individual attributes do fit into the maximum chunk size (currently 1 GB), the whole tuple is not guaranteed to fit. The flattening might be a problem in the future anyway, since there's an effort to restrict the impact of REPACK (CONCURRENTLY) on the VACUUM xmin horizon. However, as the flattening assumes scans of the TOAST relaation, the less we restrict VACUUM, the more likely it is that the TOAST attributes needed for the flattening won't be available at decoding time. (This patch also removes unnecessary field 'tupdesc' from RepackDecodingState and allocates it in the appropriate memory context.) --- src/backend/commands/cluster.c | 264 +++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 122 ++++++-- src/include/commands/cluster.h | 6 +- .../expected/repack_toast.out | 1 + .../injection_points/specs/repack_toast.spec | 7 + 5 files changed, 331 insertions(+), 69 deletions(-) diff --git a/src/backend/commands/cluster.c b/src/backend/commands/cluster.c index fe419ef808e..77e301b7c63 100644 --- a/src/backend/commands/cluster.c +++ b/src/backend/commands/cluster.c @@ -33,6 +33,7 @@ #include "postgres.h" #include "access/amapi.h" +#include "access/detoast.h" #include "access/heapam.h" #include "access/multixact.h" #include "access/relscan.h" @@ -285,6 +286,10 @@ static void apply_concurrent_update(Relation rel, HeapTuple tup, IndexInsertState *iistate, TupleTableSlot *index_slot); static void apply_concurrent_delete(Relation rel, HeapTuple tup_target); +static HeapTuple restore_tuple(BufFile *file, Relation relation, + MemoryContext cxt); +static HeapTuple adjust_toast_pointers(Relation relation, HeapTuple tup_dst, + HeapTuple tup_src, MemoryContext cxt); static HeapTuple find_target_tuple(Relation rel, ChangeDest *dest, HeapTuple tup_key, TupleTableSlot *ident_slot); @@ -2622,6 +2627,7 @@ setup_logical_decoding(Oid relid) LogicalDecodingContext *ctx; NameData slotname; RepackDecodingState *dstate; + MemoryContext oldcxt; /* * REPACK CONCURRENTLY is not allowed in a transaction block, so this @@ -2672,14 +2678,6 @@ setup_logical_decoding(Oid relid) */ ctx->reader->routine.page_read = read_local_xlog_page_no_wait; - /* - * read_local_xlog_page_no_wait() needs to be able to indicate the end of - * WAL. - */ - ctx->reader->private_data = MemoryContextAllocZero(ctx->context, - sizeof(ReadLocalXLogPageNoWaitPrivate)); - - /* Some WAL records should have been read. */ Assert(ctx->reader->EndRecPtr != InvalidXLogRecPtr); @@ -2690,18 +2688,27 @@ setup_logical_decoding(Oid relid) XLByteToSeg(ctx->reader->EndRecPtr, repack_current_segment, wal_segment_size); - dstate = palloc0_object(RepackDecodingState); - dstate->relid = relid; + /* Our private state belongs to the decoding context. */ + oldcxt = MemoryContextSwitchTo(ctx->context); /* - * Tuple descriptor may be needed to flatten a tuple before we write it to - * a file. A copy is needed because the decoding worker invalidates system - * caches before it starts to do the actual work. + * read_local_xlog_page_no_wait() needs to be able to indicate the end of + * WAL. */ - rel = table_open(relid, AccessShareLock); - dstate->tupdesc = CreateTupleDescCopy(RelationGetDescr(rel)); + ctx->reader->private_data = palloc0_object(ReadLocalXLogPageNoWaitPrivate); + dstate = palloc0_object(RepackDecodingState); + MemoryContextSwitchTo(oldcxt); + +#ifdef USE_ASSERT_CHECKING + dstate->relid = relid; +#endif + + dstate->change_cxt = AllocSetContextCreate(ctx->context, + "REPACK - change", + ALLOCSET_DEFAULT_SIZES); /* Avoid logical decoding of other relations. */ + rel = table_open(relid, AccessShareLock); repacked_rel_locator = rel->rd_locator; toastrelid = rel->rd_rel->reltoastrelid; if (OidIsValid(toastrelid)) @@ -2870,10 +2877,10 @@ static void apply_concurrent_changes(BufFile *file, ChangeDest *dest) { char kind; - uint32 t_len; Relation rel = dest->rel; TupleTableSlot *index_slot, *ident_slot; + MemoryContext apply_cxt; HeapTuple tup_old = NULL; /* TupleTableSlot is needed to pass the tuple to ExecInsertIndexTuples(). */ @@ -2883,6 +2890,14 @@ apply_concurrent_changes(BufFile *file, ChangeDest *dest) /* A slot to fetch tuples from identity index. */ ident_slot = table_slot_create(rel, NULL); + /* + * Use a separate memory context for the tuples and any memory needed to + * process them. + */ + apply_cxt = AllocSetContextCreate(TopTransactionContext, + "REPACK - apply", + ALLOCSET_DEFAULT_SIZES); + while (true) { size_t nread; @@ -2897,14 +2912,7 @@ apply_concurrent_changes(BufFile *file, ChangeDest *dest) break; /* Read the tuple. */ - BufFileReadExact(file, &t_len, sizeof(t_len)); - tup = (HeapTuple) palloc(HEAPTUPLESIZE + t_len); - tup->t_data = (HeapTupleHeader) ((char *) tup + HEAPTUPLESIZE); - BufFileReadExact(file, tup->t_data, t_len); - tup->t_len = t_len; - ItemPointerSetInvalid(&tup->t_self); - tup->t_tableOid = RelationGetRelid(dest->rel); - + tup = restore_tuple(file, rel, apply_cxt); if (kind == CHANGE_UPDATE_OLD) { Assert(tup_old == NULL); @@ -2916,7 +2924,7 @@ apply_concurrent_changes(BufFile *file, ChangeDest *dest) apply_concurrent_insert(rel, tup, dest->iistate, index_slot); - pfree(tup); + MemoryContextReset(apply_cxt); } else if (kind == CHANGE_UPDATE_NEW || kind == CHANGE_DELETE) { @@ -2940,18 +2948,28 @@ apply_concurrent_changes(BufFile *file, ChangeDest *dest) elog(ERROR, "failed to find target tuple"); if (kind == CHANGE_UPDATE_NEW) + { + /* + * If 'tup' contains TOAST pointers, they point to the old + * relation's toast. Copy the corresponding TOAST pointers for + * the new relation from the existing tuple. (The fact that we + * received a TOAST pointer here implies that the attribute + * hasn't changed.) + */ + if (HeapTupleHasExternal(tup)) + tup = adjust_toast_pointers(rel, tup, tup_exist, + apply_cxt); + apply_concurrent_update(rel, tup, tup_exist, dest->iistate, index_slot); + } else apply_concurrent_delete(rel, tup_exist); if (tup_old != NULL) - { - pfree(tup_old); tup_old = NULL; - } - pfree(tup); + MemoryContextReset(apply_cxt); } else elog(ERROR, "unrecognized kind of change: %d", kind); @@ -2968,6 +2986,7 @@ apply_concurrent_changes(BufFile *file, ChangeDest *dest) } /* Cleanup. */ + MemoryContextDelete(apply_cxt); ExecDropSingleTupleTableSlot(index_slot); ExecDropSingleTupleTableSlot(ident_slot); } @@ -3077,6 +3096,186 @@ apply_concurrent_delete(Relation rel, HeapTuple tup_target) pgstat_progress_incr_param(PROGRESS_REPACK_HEAP_TUPLES_DELETED, 1); } +/* + * Read tuple from file and store it in given memory context. + * + * External attributes are stored in separate memory chunks, in order to avoid + * exceeding MaxAllocSize - that could happen if the individual attributes are + * smaller than MaxAllocSize but the whole tuple is bigger. + */ +static HeapTuple +restore_tuple(BufFile *file, Relation relation, MemoryContext cxt) +{ + uint32 t_len; + HeapTuple tup; + MemoryContext oldcxt; + uint32 natt_ext; + List *attrs_ext = NIL; + + oldcxt = MemoryContextSwitchTo(cxt); + + /* First, read the external attributes if there are some. */ + BufFileReadExact(file, &natt_ext, sizeof(natt_ext)); + for (int i = 0; i < natt_ext; i++) + { + varlena varhdr; + char *ext_val; + Size ext_val_size; + + /* + * Read the header into properly aligned memory before accessing it. + */ + BufFileReadExact(file, &varhdr, VARHDRSZ); + ext_val_size = VARSIZE_ANY(&varhdr); + ext_val = palloc0(ext_val_size); + memcpy(ext_val, &varhdr, VARHDRSZ); + BufFileReadExact(file, ext_val + VARHDRSZ, ext_val_size - VARHDRSZ); + + attrs_ext = lappend(attrs_ext, ext_val); + } + + /* Read the tuple. */ + BufFileReadExact(file, &t_len, sizeof(t_len)); + tup = (HeapTuple) palloc(HEAPTUPLESIZE + t_len); + tup->t_data = (HeapTupleHeader) ((char *) tup + HEAPTUPLESIZE); + BufFileReadExact(file, tup->t_data, t_len); + tup->t_len = t_len; + ItemPointerSetInvalid(&tup->t_self); + tup->t_tableOid = RelationGetRelid(relation); + + /* + * If there are "external indirect" attributes, make the tuple reference + * them. + */ + if (natt_ext > 0) + { + TupleDesc desc; + Datum *attrs; + bool *isnull; + ListCell *lc; + + desc = RelationGetDescr(relation); + attrs = palloc0_array(Datum, desc->natts); + isnull = palloc0_array(bool, desc->natts); + + heap_deform_tuple(tup, desc, attrs, isnull); + + lc = list_head(attrs_ext); + for (int i = 0; i < desc->natts; i++) + { + CompactAttribute *attr = TupleDescCompactAttr(desc, i); + varlena *varlena_pointer, + *new_datum; + varatt_indirect redirect_pointer; + + /* Find the external attributes, like in store_change(). */ + if (attr->attisdropped) + continue; + if (attr->attlen != -1) + continue; + if (isnull[i]) + continue; + varlena_pointer = (varlena *) DatumGetPointer(attrs[i]); + if (!VARATT_IS_EXTERNAL_INDIRECT(varlena_pointer)) + continue; + + /* Update the attribute. */ + memset(&redirect_pointer, 0, sizeof(redirect_pointer)); + redirect_pointer.pointer = lfirst(lc); + + new_datum = (varlena *) palloc0(INDIRECT_POINTER_SIZE); + SET_VARTAG_EXTERNAL(new_datum, VARTAG_INDIRECT); + memcpy(VARDATA_EXTERNAL(new_datum), &redirect_pointer, + sizeof(redirect_pointer)); + + attrs[i] = PointerGetDatum(new_datum); + + lc = lnext(attrs_ext, lc); + } + Assert(lc == NULL); + + tup = heap_form_tuple(desc, attrs, isnull); + } + + MemoryContextSwitchTo(oldcxt); + + return tup; +} + +/* + * Copy TOAST pointers from 'tup_src' to 'tup_dst' and return the modified + * 'tup_dst'. Use 'cxt' for all memory allocations. + */ +static HeapTuple +adjust_toast_pointers(Relation relation, HeapTuple tup_dst, + HeapTuple tup_src, MemoryContext cxt) +{ + TupleDesc desc; + Datum *attrs_dst; + bool *isnull_dst; + Datum *attrs_src = NULL; + bool *isnull_src = NULL; + MemoryContext oldcxt; + HeapTuple result; + + oldcxt = MemoryContextSwitchTo(cxt); + + desc = RelationGetDescr(relation); + attrs_dst = palloc0_array(Datum, desc->natts); + isnull_dst = palloc0_array(bool, desc->natts); + + heap_deform_tuple(tup_dst, desc, attrs_dst, isnull_dst); + + for (int i = 0; i < desc->natts; i++) + { + CompactAttribute *attr = TupleDescCompactAttr(desc, i); + varlena *varlena_dst, + *varlena_src; + + if (attr->attisdropped) + continue; + if (attr->attlen != -1) + continue; + if (isnull_dst[i]) + continue; + + varlena_dst = (varlena *) DatumGetPointer(attrs_dst[i]); + if (!VARATT_IS_EXTERNAL_ONDISK(varlena_dst)) + continue; + + /* + * The first TOAST pointer? The caller can easily check if the tuple + * has external attributes(s) in general, but is not supposed to check + * specifically for TOAST. + */ + if (attrs_src == NULL) + { + attrs_src = palloc0_array(Datum, desc->natts); + isnull_src = palloc0_array(bool, desc->natts); + + heap_deform_tuple(tup_src, desc, attrs_src, isnull_src); + } + + varlena_src = (varlena *) DatumGetPointer(attrs_src[i]); + + /* + * Logical decoding only uses TOAST pointer for attributes that + * haven't changed. + */ + Assert(!isnull_src[i]); + Assert(VARATT_IS_EXTERNAL_ONDISK(varlena_src)); + + /* Copy the pointer. */ + memcpy(VARDATA_EXTERNAL(varlena_dst), VARDATA_EXTERNAL(varlena_src), + sizeof(varatt_external)); + } + result = heap_form_tuple(desc, attrs_dst, isnull_dst); + + MemoryContextSwitchTo(oldcxt); + + return result; +} + /* * Find the tuple to be updated or deleted. * @@ -3299,15 +3498,8 @@ free_index_insert_state(IndexInsertState *iistate) static void cleanup_logical_decoding(LogicalDecodingContext *ctx) { - RepackDecodingState *dstate; - - dstate = (RepackDecodingState *) ctx->output_writer_private; - - FreeTupleDesc(dstate->tupdesc); FreeDecodingContext(ctx); - ReplicationSlotDropAcquired(); - pfree(dstate); } /* diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index d0c464a98d5..707940c1127 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -12,7 +12,7 @@ */ #include "postgres.h" -#include "access/heaptoast.h" +#include "access/detoast.h" #include "commands/cluster.h" #include "replication/snapbuild.h" #include "utils/memutils.h" @@ -28,7 +28,7 @@ static void plugin_commit_txn(LogicalDecodingContext *ctx, ReorderBufferTXN *txn, XLogRecPtr commit_lsn); static void plugin_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn, Relation rel, ReorderBufferChange *change); -static void store_change(LogicalDecodingContext *ctx, +static void store_change(LogicalDecodingContext *ctx, Relation relation, ConcurrentChangeKind kind, HeapTuple tuple); void @@ -97,9 +97,8 @@ plugin_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn, dstate = (RepackDecodingState *) ctx->output_writer_private; - /* Only interested in one particular relation. */ - if (relation->rd_id != dstate->relid) - return; + /* Changes of other relation should not have been decoded. */ + Assert(RelationGetRelid(relation) == dstate->relid); /* Decode entry depending on its type */ switch (change->action) @@ -117,7 +116,7 @@ plugin_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn, if (newtuple == NULL) elog(ERROR, "incomplete insert info."); - store_change(ctx, CHANGE_INSERT, newtuple); + store_change(ctx, relation, CHANGE_INSERT, newtuple); } break; case REORDER_BUFFER_CHANGE_UPDATE: @@ -132,9 +131,9 @@ plugin_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn, elog(ERROR, "incomplete update info."); if (oldtuple != NULL) - store_change(ctx, CHANGE_UPDATE_OLD, oldtuple); + store_change(ctx, relation, CHANGE_UPDATE_OLD, oldtuple); - store_change(ctx, CHANGE_UPDATE_NEW, newtuple); + store_change(ctx, relation, CHANGE_UPDATE_NEW, newtuple); } break; case REORDER_BUFFER_CHANGE_DELETE: @@ -146,7 +145,7 @@ plugin_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn, if (oldtuple == NULL) elog(ERROR, "incomplete delete info."); - store_change(ctx, CHANGE_DELETE, oldtuple); + store_change(ctx, relation, CHANGE_DELETE, oldtuple); } break; default: @@ -164,39 +163,100 @@ plugin_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn, /* Store concurrent data change. */ static void -store_change(LogicalDecodingContext *ctx, ConcurrentChangeKind kind, - HeapTuple tuple) +store_change(LogicalDecodingContext *ctx, Relation relation, + ConcurrentChangeKind kind, HeapTuple tuple) { RepackDecodingState *dstate; + MemoryContext oldcxt; + BufFile *file; char kind_byte = (char) kind; - bool flattened = false; + List *attrs_ext = NIL; + uint32 natt_ext; dstate = (RepackDecodingState *) ctx->output_writer_private; + file = dstate->file; /* Store the change kind. */ - BufFileWrite(dstate->file, &kind_byte, 1); + BufFileWrite(file, &kind_byte, 1); + + /* Make sure there are no memory leaks. */ + oldcxt = MemoryContextSwitchTo(dstate->change_cxt); /* - * ReorderBufferCommit() stores the TOAST chunks in its private memory - * context and frees them after having called apply_change(). Therefore - * we need flat copy (including TOAST) that we eventually copy into the - * memory context which is available to decode_concurrent_changes(). + * If the tuple contains "external indirect" attributes, we need to write + * the contents to the file because we have no control over that memory. */ if (HeapTupleHasExternal(tuple)) { - /* - * toast_flatten_tuple_to_datum() might be more convenient but we - * don't want the decompression it does. - */ - tuple = toast_flatten_tuple(tuple, dstate->tupdesc); - flattened = true; - } - /* Store the tuple size ... */ - BufFileWrite(dstate->file, &tuple->t_len, sizeof(tuple->t_len)); - /* ... and the tuple itself. */ - BufFileWrite(dstate->file, tuple->t_data, tuple->t_len); + TupleDesc desc; + Datum *attrs; + bool *isnull; - /* Free the flat copy if created above. */ - if (flattened) - pfree(tuple); + desc = RelationGetDescr(relation); + attrs = palloc0_array(Datum, desc->natts); + isnull = palloc0_array(bool, desc->natts); + + heap_deform_tuple(tuple, desc, attrs, isnull); + + /* First, gather and count the "external indirect" attributes. */ + for (int i = 0; i < desc->natts; i++) + { + CompactAttribute *attr = TupleDescCompactAttr(desc, i); + varlena *varlena_pointer; + + if (attr->attisdropped) + continue; + + /* not a varlena datatype */ + if (attr->attlen != -1) + continue; + + /* no data */ + if (isnull[i]) + continue; + + /* ok, we know we have a toast datum */ + varlena_pointer = (varlena *) DatumGetPointer(attrs[i]); + + if (!VARATT_IS_EXTERNAL(varlena_pointer)) + continue; + + if (VARATT_IS_EXTERNAL_INDIRECT(varlena_pointer)) + attrs_ext = lappend(attrs_ext, varlena_pointer); + else + { + /* + * Logical decoding should not produce "external expanded" + * attributes (those actually should never appear on disk), so + * only TOASTed attribute can be seen here. + */ + Assert(VARATT_IS_EXTERNAL_ONDISK(varlena_pointer)); + } + } + natt_ext = list_length(attrs_ext); + } + else + natt_ext = 0; + + /* Write the number of external attributes. */ + BufFileWrite(file, &natt_ext, sizeof(natt_ext)); + /* ... and the attributes themselves, if there are some. */ + foreach_ptr(varlena, attr_val, attrs_ext) + { + varlena *ext_val; + Size ext_val_size; + + ext_val = detoast_external_attr(attr_val); + ext_val_size = VARSIZE_ANY(ext_val); + BufFileWrite(file, ext_val, ext_val_size); + } + + /* Finally write the tuple size ... */ + BufFileWrite(file, &tuple->t_len, sizeof(tuple->t_len)); + /* ... and the tuple itself. */ + BufFileWrite(file, tuple->t_data, tuple->t_len); + + /* Cleanup. */ + MemoryContextSwitchTo(oldcxt); + MemoryContextReset(dstate->change_cxt); } diff --git a/src/include/commands/cluster.h b/src/include/commands/cluster.h index 1b05d5d418b..34b7208de9b 100644 --- a/src/include/commands/cluster.h +++ b/src/include/commands/cluster.h @@ -65,11 +65,13 @@ typedef enum */ typedef struct RepackDecodingState { +#ifdef USE_ASSERT_CHECKING /* The relation whose changes we're decoding. */ Oid relid; +#endif - /* Tuple descriptor of the relation being processed. */ - TupleDesc tupdesc; + /* Per-change memory context. */ + MemoryContext change_cxt; /* The current output file. */ BufFile *file; diff --git a/src/test/modules/injection_points/expected/repack_toast.out b/src/test/modules/injection_points/expected/repack_toast.out index 4f866a74e32..b56dde134f8 100644 --- a/src/test/modules/injection_points/expected/repack_toast.out +++ b/src/test/modules/injection_points/expected/repack_toast.out @@ -13,6 +13,7 @@ step change: UPDATE repack_test SET j=get_long_string() where i=2; DELETE FROM repack_test WHERE i=3; INSERT INTO repack_test(i, j) VALUES (4, get_long_string()); + UPDATE repack_test SET i=3 where i=1; step check2: INSERT INTO relfilenodes(node) diff --git a/src/test/modules/injection_points/specs/repack_toast.spec b/src/test/modules/injection_points/specs/repack_toast.spec index b48abf21450..b878b198971 100644 --- a/src/test/modules/injection_points/specs/repack_toast.spec +++ b/src/test/modules/injection_points/specs/repack_toast.spec @@ -74,10 +74,17 @@ teardown session s2 step change +# Separately test UPDATE of both plain ("i") and TOASTed ("j") attribute. In +# the first case, the new tuple we get from reorderbuffer.c contains "j" as a +# TOAST pointer, which we need to update so it points to the new heap. In the +# latter case, we receive "j" as "external indirect" value - here we test that +# the decoding worker writes the tuple to a file correctly and that the +# backend executing REPACK manages to restore it. { UPDATE repack_test SET j=get_long_string() where i=2; DELETE FROM repack_test WHERE i=3; INSERT INTO repack_test(i, j) VALUES (4, get_long_string()); + UPDATE repack_test SET i=3 where i=1; } # Check the table from the perspective of s2. step check2 -- 2.47.3 --k4rn5ob3nx2ufkij Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v40-0004-Use-BulkInsertState-when-copying-data-to-the-new.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v53 1/7] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 59 ++++++++++++++++++--- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 131 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a6738e120c7 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1160,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1177,14 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (!db_specific || + NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1199,11 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1259,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1287,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1506,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --qr3jlalmmcpkiodg Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v53-0002-Fix-a-few-problems-in-index-build-progress-repor.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-04 15:16 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-04 15:16 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 18 +++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 5 ++ src/backend/replication/logical/snapbuild.c | 52 ++++++++++++++++--- .../pgoutput_repack/pgoutput_repack.c | 7 +++ src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 14 ++++- src/include/access/genam.h | 8 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 21 files changed, 144 insertions(+), 21 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 2be5d8d4bd9..1353d004aac 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -382,7 +382,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20a0fe70ad..89043a03497 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -289,6 +289,11 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* + * Assume true for safety, the startup callback can change that. + */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..054a7b16f43 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -170,7 +171,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1138,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,7 +1152,7 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else @@ -1166,8 +1169,13 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * (see SnapBuildCommitTxn). Because of this, xmax can be lower than * xmin, which looks odd but is correct and actually more efficient, since * we hit fast paths in heapam_visibility.c. + * + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. That would be bad + * because we might no longer have older XIDs in ->committed. */ - builder->xmin = running->oldestRunningXid; + if (NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + builder->xmin = running->oldestRunningXid; /* Remove transactions we don't need to keep track off anymore */ SnapBuildPurgeOlderTxn(builder); @@ -1182,7 +1190,10 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * the record we're reading now. */ xmin = ReorderBufferGetOldestXmin(builder->reorder); - if (xmin == InvalidTransactionId) + /* + * Like above, do not let slot xmin go backwards. + */ + if (xmin == InvalidTransactionId && !db_specific) xmin = running->oldestRunningXid; elog(DEBUG3, "xmin: %u, xmax: %u, oldest running: %u, oldest xmin: %u", builder->xmin, builder->xmax, running->oldestRunningXid, xmin); @@ -1238,7 +1249,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1277,28 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we should only keep track of transactions running in the current + * database, we need transaction info from exactly that + * database. Invalid 'dbid' (all databases) would satisfy our needs + * too, but it could make us wait unnecessarily for completion of + * transactions running in other databases. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1499,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c index 221260ca0a8..bb3a880a4c3 100644 --- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c +++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c @@ -52,6 +52,13 @@ repack_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt, /* Probably unnecessary, as we don't use the SQL interface ... */ opt->output_type = OUTPUT_PLUGIN_BINARY_OUTPUT; + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + opt->need_shared_catalogs = false; + if (ctx->output_plugin_options != NIL) { ereport(ERROR, diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..82552a97997 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index ccded021433..f5f3edc63fd 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -93,7 +93,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, struct xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - struct xl_running_xacts *running); + struct xl_running_xacts *running, + boool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH v54 1/5] Introduce an option to make logical replication database specific. @ 2026-04-05 07:51 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-05 07:51 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 8 ++- src/backend/replication/logical/logical.c | 3 ++ src/backend/replication/logical/snapbuild.c | 54 +++++++++++++++++++-- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 ++++++++- src/backend/storage/ipc/standby.c | 14 +++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 128 insertions(+), 19 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9e8999bbb61..1a6c1456d2c 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7731,7 +7731,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..4299d0bc867 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,13 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..8ef2326c66d 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running, bool db_specific); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -1136,7 +1146,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1149,12 +1160,21 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact if (builder->state < SNAPBUILD_CONSISTENT) { /* returns false if there's no point in performing cleanup just yet */ - if (!SnapBuildFindSnapshot(builder, lsn, running)) + if (!SnapBuildFindSnapshot(builder, lsn, running, db_specific)) return; } else SnapBuildSerialize(builder, lsn); + /* + * If database specific transaction info was used during startup, the info + * for the whole cluster can make xmin go backwards. The code below + * probably does not expect that, let's wait with the cleanup for the next + * record. + */ + if (!NormalTransactionIdFollows(running->oldestRunningXid, builder->xmin)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1238,7 +1258,8 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact * using the xl_running_xacts record. */ static bool -SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { /* --- * Build catalog decoding snapshot incrementally using information about @@ -1265,6 +1286,25 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn * --- */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + return false; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + accessSharedCatalogsInDecoding = false; + } + /* * xl_running_xacts record is older than what we can use, we might not * have all necessary catalog rows anymore. @@ -1465,7 +1505,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..9533515a63b 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1762,7 +1762,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --cdhh4t7ukb6tnjoq Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v54-0002-Rename-cluster.c-h-repack.c-h.patch" ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-06 08:49 Antonin Houska <[email protected]> 0 siblings, 0 replies; 334+ messages in thread From: Antonin Houska @ 2026-04-06 08:49 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch adds a new option to logical replication output plugin, to declare that it does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in the plugin for logical replication too, however that would need thorough analysis of that plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 +- doc/src/sgml/logicaldecoding.sgml | 4 ++ src/backend/access/index/genam.c | 8 +++ src/backend/access/rmgrdesc/standbydesc.c | 2 + src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/decode.c | 16 +++++- src/backend/replication/logical/logical.c | 3 + src/backend/replication/logical/snapbuild.c | 64 ++++++++++++++++++++- src/backend/replication/slot.c | 2 +- src/backend/storage/ipc/procarray.c | 23 +++++++- src/backend/storage/ipc/standby.c | 24 +++++++- src/include/access/genam.h | 7 +++ src/include/access/xlog_internal.h | 2 +- src/include/replication/output_plugin.h | 1 + src/include/replication/snapbuild.h | 3 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 +- src/include/storage/standbydefs.h | 1 + 20 files changed, 157 insertions(+), 18 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/doc/src/sgml/logicaldecoding.sgml b/doc/src/sgml/logicaldecoding.sgml index 6dc49108997..28089d1053c 100644 --- a/doc/src/sgml/logicaldecoding.sgml +++ b/doc/src/sgml/logicaldecoding.sgml @@ -959,6 +959,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; </programlisting> <literal>output_type</literal> has to either be set to @@ -969,6 +970,9 @@ typedef struct OutputPluginOptions also be called for changes made by heap rewrites during certain DDL operations. These are of interest to plugins that handle DDL replication, but they require special handling. + <literal>need_shared_catalogs</literal> can be set to false if you are + sure the plugin functions do not access shared system catalogs. It can + speed up creation of replication slots that use this plugin. </para> <para> diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..44df2605068 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -394,6 +394,14 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index b82af9a85c0..3f08a832ca6 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7735,7 +7735,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c index 57aaef57c61..49a59605515 100644 --- a/src/backend/replication/logical/decode.c +++ b/src/backend/replication/logical/decode.c @@ -381,7 +381,15 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) { xl_running_xacts *running = (xl_running_xacts *) XLogRecGetData(r); - SnapBuildProcessRunningXacts(builder, buf->origptr, running); + + /* + * If the plugin does not access shared catalogs, only keep + * track of transactions in the current database. This is + * currently the only use case for database-specific running + * xacts record. + */ + SnapBuildProcessRunningXacts(builder, buf->origptr, running, + !ctx->options.need_shared_catalogs); /* * Abort all transactions that we keep track of, that are @@ -391,8 +399,12 @@ standby_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf) * all running transactions which includes prepared ones, * while shutdown checkpoints just know that no non-prepared * transactions are in progress. + * + * The database-specific records might work here too, but it's + * not their purpose. */ - ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); + if (!OidIsValid(running->dbid)) + ReorderBufferAbortOld(ctx->reorder, running->oldestRunningXid); } break; case XLOG_STANDBY_LOCK: diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index f20d0c542f3..8ceaf64d164 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -285,6 +285,9 @@ StartupDecodingContext(List *output_plugin_options, ctx->write = do_write; ctx->update_progress = update_progress; + /* Assume shared catalog access. The startup callback can change it. */ + ctx->options.need_shared_catalogs = true; + ctx->output_plugin_options = output_plugin_options; ctx->fast_forward = fast_forward; diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..a10e8c0ca77 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -154,6 +155,14 @@ static ResourceOwner SavedResourceOwnerDuringExport = NULL; static bool ExportInProgress = false; +/* + * If a backend is going to do logical decoding and the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ->committed and ->catchange manipulation */ static void SnapBuildPurgeOlderTxn(SnapBuild *builder); @@ -170,7 +179,8 @@ static inline bool SnapBuildXidHasCatalogChanges(SnapBuild *builder, Transaction uint32 xinfo); /* xlog reading helper functions for SnapBuildProcessRunningXacts */ -static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running); +static bool SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, + xl_running_xacts *running); static void SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff); /* serialization functions */ @@ -226,6 +236,9 @@ AllocateSnapshotBuilder(ReorderBuffer *reorder, MemoryContextSwitchTo(oldcontext); + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + return builder; } @@ -244,6 +257,9 @@ FreeSnapshotBuilder(SnapBuild *builder) builder->snapshot = NULL; } + /* The default is that shared catalog are used. */ + accessSharedCatalogsInDecoding = true; + /* other resources are deallocated via memory context reset */ MemoryContextDelete(context); } @@ -1136,7 +1152,8 @@ SnapBuildXidHasCatalogChanges(SnapBuild *builder, TransactionId xid, * anymore. */ void -SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running) +SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *running, + bool db_specific) { ReorderBufferTXN *txn; TransactionId xmin; @@ -1148,6 +1165,33 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact */ if (builder->state < SNAPBUILD_CONSISTENT) { + /* + * To reduce the potential for unnecessarily waiting for completion of + * unrelated transactions, the caller can declare that only + * transactions of the current database are relevant at this + * stage. + */ + if (db_specific) + { + /* + * If we must only keep track of transactions running in the current + * database, we need transaction info from exactly that database. + */ + if (running->dbid != MyDatabaseId) + { + LogStandbySnapshot(MyDatabaseId); + + return; + } + + /* + * We'd better be able to check during scan if the plugin does not + * lie. + */ + if (accessSharedCatalogsInDecoding) + accessSharedCatalogsInDecoding = false; + } + /* returns false if there's no point in performing cleanup just yet */ if (!SnapBuildFindSnapshot(builder, lsn, running)) return; @@ -1155,6 +1199,16 @@ SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, xl_running_xact else SnapBuildSerialize(builder, lsn); + /* + * Database specific transaction info may exist to reach CONSISTENT state + * faster, however the code below makes no use of it. Moreover, such + * record might cause problems because the following normal (cluster-wide) + * record can have lower value of oldestRunningXid. In that case, let's + * wait with the cleanup for the next regular cluster-wide record. + */ + if (OidIsValid(running->dbid)) + return; + /* * Update range of interesting xids based on the running xacts * information. We don't increase ->xmax using it, because once we are in @@ -1465,7 +1519,11 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + /* + * If the last transaction info was about specific database, so needs + * to be the next one - at least until we're in the CONSISTENT state. + */ + LogStandbySnapshot(running->dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index 21a213a0ebf..a1f37e59dbc 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -1756,7 +1756,7 @@ ReplicationSlotReserveWal(void) XLogRecPtr flushptr; /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + flushptr = LogStandbySnapshot(InvalidOid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index f540bb6b23f..9299bcebbda 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2623,9 +2623,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2700,6 +2702,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2750,6 +2764,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2783,6 +2803,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..29af7733948 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,22 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that + * database. snapbuild.c can use such running xacts information for faster + * startup, but it still needs normal (cluster-wide) during the actual + * decoding - see standby_decode() and SnapBuildProcessRunningXacts() for + * details. Other processes (e.g. checkpointer) issue the cluster-wide records + * whether logical decoding is active or not. + * + * Please be careful about using this argument for other purposes. In + * particular, physical replication *must* ignore the database-specific + * records, exactly because they do not cover the whole cluster - see + * standby_redo(). * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1333,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1377,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..c9a52277be1 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,13 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; + +/* + * Keep track of whether logical decoding in this backend promised not to + * access shared catalogs, as a safety check. Somewhat misplaced, but ... + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 10c18d39ff8..13ae3ad4fbb 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -32,7 +32,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h index 842fcde67f9..917f3cff232 100644 --- a/src/include/replication/output_plugin.h +++ b/src/include/replication/output_plugin.h @@ -27,6 +27,7 @@ typedef struct OutputPluginOptions { OutputPluginOutputType output_type; bool receive_rewrites; + bool need_shared_catalogs; } OutputPluginOptions; /* diff --git a/src/include/replication/snapbuild.h b/src/include/replication/snapbuild.h index a22a83a2f23..d02530a912a 100644 --- a/src/include/replication/snapbuild.h +++ b/src/include/replication/snapbuild.h @@ -92,7 +92,8 @@ extern void SnapBuildProcessNewCid(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn, xl_heap_new_cid *xlrec); extern void SnapBuildProcessRunningXacts(SnapBuild *builder, XLogRecPtr lsn, - xl_running_xacts *running); + xl_running_xacts *running, + bool db_specific); extern void SnapBuildSerializationPoint(SnapBuild *builder, XLogRecPtr lsn); extern bool SnapBuildSnapshotExists(XLogRecPtr lsn); diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index d718a5b542f..ec89c448220 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -47,7 +47,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 334+ messages in thread
end of thread, other threads:[~2026-04-06 08:49 UTC | newest] Thread overview: 334+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2026-03-09 10:35 [PATCH v40 3/4] Serialize decoded tuples without flattening. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH v53 1/7] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-04 15:16 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-05 07:51 [PATCH v54 1/5] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-06 08:49 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]>
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